Exploring the Concept of Elevated Vegetative Systems for Shading on Roofs to Reduce Urban Heat Island

Shading is a mechanism that has been providing a cooling effect for buildings for many years. It blocks solar radiation from being absorbed by the building envelope layers. A plant-based shading approach has been proven beneficial in reducing environmental temperatures resulting from urban heat island (UHI) gains. Vegetation in the form of trees, green roofs, and green facades has been incorporated in building design to minimize the UHI effect. This report outlines the alternative to green roofs for cooling building rooftops through the development of elevated horizontal and vertical vegetation systems so that it can be assessed how much shading can be provided with this substitute. Elevated vegetation systems not only provide shading but also form a buffer space between the roof layer and vegetation and hence improve macro- and microclimate. The study uses computer simulations via SketchUp & AutoCAD. Manual calculations were carried out to evaluate the amount of shadow formed by the two systems at certain times of the day. The performance of three climbing plants was also assessed on these systems and compared. Results show that a horizontal raised system covered with Virginia Creeper produces a significant amount of shadow, i.e., 60% of the roof will remain under shade in summers. For predicting the surface temperature reduction, a systemic review of data was explored and analyzed through IBM SPSS 2022, and it is concluded that the reduction in surface temperatures ranging from a minimum of 6.24 to 12.8°C (with SD +/- 4.2 and +/- 6.37) respectively can be achieved.<p></p>